An unarmed black man killed by a white Oklahoma officer who was responding to a stalled vehicle can be seen in police video walking away from officers and toward his SUV with his hands up before he approaches the driver's side door, where he drops to the ground after being shocked with a stun gun then fatally shot.

In Tulsa police helicopter footage that was among several clips released Monday showing the shooting of 40-year-old Terence Crutcher and its aftermath, a man in the helicopter that arrives above the scene as Crutcher walks to the vehicle can be heard saying "time for a Taser.'' He then says: "That looks like a bad dude, too. Probably on something.''

Police Chief Chuck Jordan announced before the video and audio recordings' release that Crutcher had no weapon on him or in his SUV when he was shot Friday. It's not clear from the footage what led Betty Shelby, the officer who fired the fatal shot, to draw her gun or what orders officers might have given Crutcher. Local and federal investigations are underway to determine whether criminal charges are warranted in the shooting or if Crutcher's civil rights were violated.

Crutcher's twin sister, Tiffany Crutcher, called for charges Monday.

"The big bad dude was my twin brother. That big bad dude was a father,'' she said. "That big bad dude was a son. That big bad dude was enrolled at Tulsa Community College, just wanting to make us proud. That big bad dude loved God. That big bad dude was at church singing with all of his flaws, every week. That big bad dude, that's who he was.''

Police video shows Crutcher walking toward his SUV that is stopped in the middle of the road. His hands are up and a female officer is following him. As Crutcher approaches the driver's side of the SUV, three male officers walk up and Crutcher appears to lower his hands and place them on the vehicle. The officers surround him, making it harder to see his actions from the dashboard camera's angle.

Crutcher can be seen dropping to the ground. Someone on the police radio says, "I think he may have just been tasered.'' One of the officers near Crutcher backs up slightly.

Then almost immediately, someone can be heard yelling, "Shots fired!'' Crutcher's head then drops, leaving him completely lying out in the street.

After that, someone on the police radio can be heard saying, "Shots fired. We have one suspect down.''

The shooting comes just four months after former Tulsa County volunteer deputy Robert Bates was sentenced to four years in prison on a second-degree manslaughter conviction in the 2015 death of an unarmed black man. Shelby worked as a Tulsa County sheriff's deputy for four years before joining the Tulsa Police Department in December 2011, officials said. She has been placed on paid leave.

The initial moments of Crutcher's encounter with police are not shown in the footage. Shelby did not activate her patrol car's dashcam, said police spokeswoman Jeanne MacKenzie, and the ground-level video released Monday came from the car of a second officer who arrived at the scene.

Initial police briefings indicated Crutcher was not obeying officers' commands, but MacKenzie said Monday she didn't know what Crutcher was doing that prompted police to shoot. Two 911 calls described an SUV that had been abandoned in the middle of the road. One unidentified caller said the driver was acting strangely, adding, "I think he's smoking something.''

After the shooting, Crutcher could be seen lying on the side of the road, blood pooling around his body, for nearly two minutes before anyone checked on him. When asked why police did not provide immediate assistance once Crutcher was down, MacKenzie said, "I don't know that we have protocol on how to render aid to people.''

The American Civil Liberties Union of Oklahoma, which also called for charges, said Crutcher was left to bleed while officers stood by. The group's executive director, Ryan Kiesel, said Crutcher's death shows "how little regard'' Tulsa police have for the community's minorities.

With relations between police and blacks in Tulsa already uneasy, the community needs to be the place where change happens, Tiffany Crutcher said.

"This is bigger than us right here. We're going to stop it right here,'' she said.

U.S. Attorney Danny C. Williams said the Department of Justice's civil rights investigation into the shooting will be separate from a local one into whether criminal charges should be filed.

"The Justice Department is committed to investigating allegations of force by law enforcement officers and will devote whatever resources are necessary to ensure that all allegations of serious civil rights violations are fully and completely investigated,'' he said.

Speaking Monday in Tulsa, civil rights attorney Benjamin Crump said Crutcher committed no crime and gave officers no reason to shoot him.

"When unarmed people of color break down on the side of the road, we're not treated as citizens needing help. We're treated as, I guess, criminals - suspects that they fear,'' said Crump, who is representing Crutcher's family just as he did relatives of Trayvon Martin, an unarmed, black Florida teenager who was fatally shot by a neighborhood watch volunteer in 2012.

He said Tulsa police drew their own conclusions about Crutcher.

"So I guess it's a crime now to be a big black man,'' Crump said. "My God, help us.''